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Old 11-23-2009, 01:37 AM   #1
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Default How high should it rev?

First off, i briefly searched and could not find this. If someone else does, cause my search skills fail, my bad in advance.

My question is how high should someone set the rev limiter on a modified Miata. I am talking about a Miata with a built engine, with stronger rods and low compression pistons and all that. I would assume that it could most definitely be set higher than stock but how much higher.

-P.S. this is all in theory i don't have a Miata with a built engine that i would like to raise the rev limiter on, just wondering.
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Old 11-23-2009, 01:46 AM   #2
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if you have rods and upgraded, springs then 9000 rpm isnt out of the question.
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Old 11-23-2009, 01:48 AM   #3
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Would it be practical to set it that high though. I mean where would you probably be making max power with that kind of setup.
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Old 11-23-2009, 01:57 AM   #4
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that my friend depends on a great many things. size of your turbo, can it flow enough? head flow, can you cram enough through it? cam specs, is it open long and wide enough to cram enough through it? to make signifigant enough power to be able to really use the extra rpm you probably arent talking a very street friendly car. if that dosent matter then have at it! just dont expect it to have the dyno curve of a dodge viper....
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Old 11-23-2009, 02:08 AM   #5
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Quote:
Originally Posted by halfdemonpyro View Post
that my friend depends on a great many things. size of your turbo, can it flow enough? head flow, can you cram enough through it? cam specs, is it open long and wide enough to cram enough through it? to make signifigant enough power to be able to really use the extra rpm you probably arent talking a very street friendly car. if that dosent matter then have at it! just dont expect it to have the dyno curve of a dodge viper....
holly **** best newb post ever. He is correct what size turbo are you running etc. Becouse stock there is no need to rev that high.
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Old 11-23-2009, 03:44 AM   #6
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9000 rpm sounds like a bad idea to me, even with a built bottom end and a built head, the rod ratio is just not thats good and I think piston slap would tear it up quickly.
I wouldnt want to rev much past 8 unless youre some how dramatically improving the rod ratio (short deck pistons or deck plate with custom long rods)
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Old 11-23-2009, 11:00 AM   #7
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meh markp did 8500 all day and ccpull did similiar range with no problem, our rod ratio isnt that horrible boogie.
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Old 11-23-2009, 11:48 AM   #8
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I had a 383 that saw 8K every morning on my comute to the race track, I don't rember what the rod ratio was but I bet it was worse off than our motors. As I recall piston slap only happens when there is exesive clearances, like the first LS motors, I've only heard it on a cold motor, once its warm it normaly goes away with expantion.
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Old 11-23-2009, 12:13 PM   #9
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Dyno the car, when the hp starts to fall off the deep end set your rev limit there. Simple as that. Unless your running a built head and custom intake manifold ect your looking at 8k likely, after that your just slowing down.
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Old 11-23-2009, 12:29 PM   #10
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Piston slap is an issue of piston to wall clearance. The bad rod ratio wears out the bore surface as it tries to cram the piston skirt through the side of the block, which kills ring seal faster than a better rod ratio would. That is in addition to all the other problems involved with a bad rod/stroke ratio, including low dwell time at TDC between the compression and power strokes, necessitating non optimum timing, etc.

That said, you simply can't cram enough valve lift into the BP valve train to take advantage of really high rpm. Anything over ~8500 rpm is a waste of your time...
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Old 11-23-2009, 12:57 PM   #11
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Quote:
Originally Posted by dc2696 View Post
Dyno the car, when the hp starts to fall off the deep end set your rev limit there. Simple as that. Unless your running a built head and custom intake manifold ect your looking at 8k likely, after that your just slowing down.
+1 its all about were you motor is efficient.
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Old 11-23-2009, 03:04 PM   #12
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Quote:
Originally Posted by vehicular View Post
Piston slap is an issue of piston to wall clearance. The bad rod ratio wears out the bore surface as it tries to cram the piston skirt through the side of the block, which kills ring seal faster than a better rod ratio would. That is in addition to all the other problems involved with a bad rod/stroke ratio, including low dwell time at TDC between the compression and power strokes, necessitating non optimum timing, etc.

That said, you simply can't cram enough valve lift into the BP valve train to take advantage of really high rpm. Anything over ~8500 rpm is a waste of your time...
+1

I dont tink itll grenade at 8500 rpm,but Im pretty sure it'll taper the cylinders pretty quickly. I wouldnt want to build a motor and have it start smoking and loosing compression after a few thousand miles of abuse.
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Old 11-23-2009, 05:43 PM   #13
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I usually rev mine until it's a few feet off the ground. That's good nuff.
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